Texas Instruments AM335x
========================

The Texas Instruments AM335x SoCs have a two-stage boot process. The first stage
loader, also known as MLO is loaded by the ROM code. The MLO loads the second stage
loader from the same medium.

Building barebox
----------------

Booting with barebox on the TI AM335x is a two-stage process and unlike
more recently added SoCs, requires building barebox twice, each time
with a different defconfig:

* ``omap_defconfig`` for the regular (second-stage) barebox image
* For the MLO first-stage, either ``am335x_mlo_sdmmc_defconfig`` for
  SD/eMMC or ``am335x_mlo_rawflash_defconfig`` for raw NOR/NAND.

The resulting images will be placed under ``images/``:

::

  barebox-am33xx-afi-gf.img
  barebox-am33xx-afi-gf-mlo.img
  barebox-am33xx-beaglebone.img
  barebox-am33xx-beaglebone-mlo.img
  barebox-am33xx-phytec-phycore-mlo-256mb.img
  barebox-am33xx-phytec-phycore-mlo-128mb.img
  barebox-am33xx-phytec-phycore-mlo-512mb.img
  barebox-am33xx-phytec-phycore-mlo-2x512mb.img
  barebox-am33xx-phytec-phyflex-mlo-256mb.img
  barebox-am33xx-phytec-phyflex-mlo-512mb.img
  barebox-am33xx-phytec-phycore.img
  barebox-am33xx-phytec-phycore-no-spi.img
  barebox-am33xx-phytec-phyflex.img

Some boards come in different variants, make sure to pick the correct one.

Size Constraints
^^^^^^^^^^^^^^^^

As the MLO needs to setup DRAM first, it must fit into the 109KiB
of available on-Chip SRAM. Depending on the boards, drivers and general
features enabled by your config, barebox may exceed this size resulting
in an error message during build, e.g.::

  images/start_am33xx_myirtech_sram.pblb size 111800 > maximum size 111616

If you run into this issue, consider disabling some unneeded config options
for the MLO via ``make menuconfig`` and try again.
The ``am335x_mlo_sdmmc_defconfig`` and ``am335x_mlo_rawflash_defconfig``
defconfigs do just that by disabling ``CONFIG_MTD`` and ``CONFIG_MCI``,
respectively.

Starting and updating barebox
-----------------------------

SPI NOR and NAND
^^^^^^^^^^^^^^^^

The regular board images can be started from another bootloader, see
:ref:`second_stage`. The board should provide update handlers
to update (or initially install) barebox on SPI NOR or NAND, see :ref:`update`.

SD/MMC
^^^^^^

To start barebox from SD/MMC prepare a card with a FAT filesystem. Copy the MLO
file for your board to the card and name it ``MLO``. Copy the regular image
for your board to the card and name it ``barebox.bin``.

AM335x Boards
-------------

.. toctree::
  :glob:
  :maxdepth: 1

  am335x/*